Technical Field
The present disclosure relates to an electronic power module provided with a packaging structure with enhanced thermal dissipation and to a method for manufacturing the electronic power module.
Description of the Related Art
As is known, in the manufacture of semiconductor devices, packaging is the final step that transforms a processed substrate, including electronic or electromechanical functional elements, into a component that may be mounted on a printed circuit board (PCB). The package provides a protection for the substrate and provides the electrical connections through which it is possible to supply signals to the functional elements and acquire signals coming therefrom.
To provide for an ever-increasing integration and reduction in size, the packaging methods currently used include wafer-level packaging (WLP) and 3D packaging. Further solutions envisage surface-mount devices (SMDs), which enable a further reduction of the dimensions of the package and the assembly costs.
In addition to the contained dimensions, the package, in particular for power devices, may guarantee supply of peak powers of some kilowatts and at the same time dissipation of several hundreds of watts. The package for power devices should consequently meet precise specifications both as regards the materials used and as regards the mutual arrangement of the elements that make then up. In the prior art it is known to provide an electronic device 1 of the type illustrated in lateral cross-sectional view in FIG. 1, where a case 10, provided with a side wall 2, typically of plastic material, and with a base plate 4, typically of copper, houses inside it a three-dimensional assembly comprising a bottom substrate 6, one or more dice 8 arranged on the bottom substrate 6, and a top substrate 9, which extends over the dice 8. The top substrate 9 is mechanically and electrically coupled to the bottom substrate 6 by solder balls 12. Likewise, also the dice 8 are arranged in appropriate housings of the bottom substrate 6 and are mechanically and electrically coupled to conductive paths of the top substrate 9 by solder balls 13. The dice 8 are coupled to the bottom substrate 6 by a lead-free solder paste or solder pre-form, typically made up of a SnAgCu alloy.
According to one embodiment, the dice 8 integrate, respectively, an IGBT and a diode, operatively coupled together in antiparallel configuration. The top substrate 9 and the bottom substrate 6 are of a direct-bonded-copper (DBC) type (or the like). DBC technology has been developed to provide for direct bonding of ceramic substrates with relatively thick copper laminas, without the addition of further bonding materials. DBC substrates are typically used for power circuits/modules. In greater detail, the DBC substrate is constituted by an insulating layer of ceramic material, typically alumina (Al2O3) or aluminum nitride (AlN), to which two metal layers are made to adhere, in particular of pure copper (Cu-OFE: 99.99%), in the form of laminas, by a high-temperature process. The final result is an intimate bonding between the copper laminas and the intermediate ceramic layer. Currently, this type of substrate is widely used for mounting components in electronic power circuits in so far as the intermediate ceramic layer guarantees good electrical insulation but at the same time enables good transfer of heat outwards. The conductive paths for connection of the components mounted on said substrates are obtained by etching the copper layer until the insulating ceramic layer is reached, thus forming conductive regions (paths) insulated from one another.
However, the use of the solder balls for mutual coupling between the substrates and for coupling between the dice and the substrates is the cause of an excessive thickness of the resulting stack, as well as of introduction of parasitic effects that are generated on account of the presence of the melting regions between the balls and the substrates.
Furthermore, embodiments of a known type entail long process steps in terms of manufacturing time, causing a reduction of the production efficiency.